The invention relates to the provision of digital audio or video products, for example over a network or in a pre-purchase listening or viewing kiosk. More especially, but not exclusively, the invention relates to the sale of such products over a public network, such as the Internet or other similar public communication systems.
A variety of techniques collectively known as digital watermarking has been developed to address the issue of unauthorized or illegal copying of digital video and audio products. Some such techniques result in a copied product being unviewable or inaudible. Other techniques block the copying of a watermarked original by open-circuiting the input stage of a video recorder (VCR) or other recording device when the correct watermark is not detected. Other techniques encode the source purchaser, or other information, to enable identification and tracking of unauthorized copies.
Many digital watermarking techniques are specifically directed to copying from a physical recording medium, such as a compact disc (CD) or a digital video disc (DVD). However, the transfer of digital data streams between nodes of a network raises different issues as will now be described by way of an example.
Conventionally, in a record store, it is possible for a customer to listen to an audio product prior to purchase for pre-purchase evaluation. This has proven to be an effective method for promoting sales and ensuring customer satisfaction with purchased products. However, in the context of Internet sales of audio or video products, a customer is typically shopping at home or in another comfortable environment with an audio or video reproduction system or in an Internet supported kiosk. In such an environment, unrestricted pre-purchase listening or viewing may compromise the purchase itself.
A customer who abuses the system in this way would however not be making a copy of the audio or video product. In effect, the seller would be copying the product by transmitting it to the potential buyer over the network. Conventional digital watermarking techniques would be ineffective, since there is no copying taking place.
It is thus an aim of the invention to provide means by which a potential purchaser of a video or audio product can sample the product without compromising the purchase.